I'd use a Map in GHC 6.4: count xs = toList $ fromListWith (+) (zip xs (repeat 1)) or a FiniteMap in earlier versions: count xs = fmToList $ addListToFM_C (+) emptyFM (zip xs (repeat 1)) both of these seem to be quite fast.
- Cale On 4/28/05, Dmitry Vyal <[EMAIL PROTECTED]> wrote: > Hello everybody. > > I have a long list consisted of a small number (about a dozen) of > elements repeating in random pattern. I know all the possible elements. > I need to count number of occurences of each particular element and to > do i quickly. > > For example > quick_func Eq a => [a] -> [(a,Int)] > quick_func [1,2,3,1,2,9,1,9] == [(1,3),(2,2),(3,1),(9,2)] > > According to profiler this function is the bottle-neck in my sluggish > program so I really need to speed it up. > > Any proposals? > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
